Embodiments described herein relate generally to ventilation of a combustion engine. More specifically, embodiments described herein relate to a ventilation system for blow-by gas in a combustion engine.
During operation of a combustion engine, gas is pressed out of the combustion chamber and into a crankcase through a gap between a piston ring and a cylinder wall. Gas may also come from valve stem seals and turbocharger seals. This gas, which includes hydrocarbon gases, water vapor, and a small amount of entrained liquid oil, is called blow-by gas. Unless removed from the crankcase, the blow-by gas increases the pressure inside the crankcase.
Conventionally, the blow-by gas may be vented from the crankcase with a crankcase ventilation system, also called a crankcase breather system. In an open crankcase ventilation system, the crankcase breather system vents to the atmosphere. Blow-by gas is one component of the vehicle's overall emissions, and as such, is an emission that the industry attempts to mitigate. Further, blow-by gas can produce noxious odors, which may present an issue when the vehicle is stationary.
Another conventionally known crankcase ventilation system is a closed crankcase breather system, where the blow-by gas can be vented back to the engine, for example by first being vented to a turbocharger compressor. Venting blow-by gas to the engine intake/turbocharger compressor inlet can potentially contaminate the air intake hardware of the engine/turbocharger compressor. Under high temperatures and high loading of blow-by gases, the oil entrained in the blow-by gas can harden and stick to the engine/turbocharger compressor. The hardening and sticking process of the oil from the blow-by gas is known as coking, which can reduce turbocharger compressor efficiency, thereby increasing engine emissions, and ultimately lead to failure of the engine/turbocharger compressor.